1. Field of the Invention
The present invention relates to a solvent-less O/W type emulsion. More particularly, the present invention relates to a solvent-less O/W type emulsion which exhibits a high stability in storage and employment and optionally includes a particulate solid material stably and uniformly dispersed in the emulsion.
2. Description of the Related Art
It is known that some medicaments and agricultural chemicals must exhibit a high sustained-releasing property and/or a diffusing property, as a function thereof.
For example, with respect to the production of sustained release capsules, Japanese Unexamined Patent Publications No. 59-230,635 and No. 59-159,177 disclose coacervation methods, and Japanese Unexamined Patent Publications No. 59-172,653, and 59-162,943 disclose drying-in-liquid methods, phase separation methods and spray-drying methods. Also, an agricultural chemical-producing method using a microcapsule-forming technology for the purpose of extending a effect-retaining time by a sustained release effect or of stabilizing the agricultural effective component is known. For example, various processes for producing microcapsules containing an agricultural chemical, by using, as a water-soluble capsule-forming material, gelatin (for example, Japanese Unexamined Patent Publication No. 50-99,963), polyamide, polyurethane, polyurea or polyester resin (Japanese Unexamined Patent Publication No. 54-135,671), polyvinyl acetate or polyvinyl ether resin (Japanese Unexamined Patent Publication No. 55-92,136), polyurethane-polyurea resin (Japanese Unexamined Patent Publication No. 54-91,591), polyamide-polyurea resin (Japanese Unexamined Patent Publication No. 48-4,643), or resinous prepolymer-water-soluble cationic urea resin (Japanese Unexamined Patent Publication No. 2-29,642), are known. Also, Japanese Unexamined Patent Publication No. 7-64,682 discloses a process for producing an aqueous suspension of microcapsules. These prior art processes are, however, disadvantageous in that the formation of the microcapsules is complicated, and the resultant products are unstable in performance thereof due to dispersion in thickness and/or in failure rate of the micro-capsules.
On other hand, with respect to the diffusion performance, various suspension-producing processes are known. For example, Japanese Examined Patent Publication No. 46-20,519 discloses a process for producing an aqueous suspension by wet-pulverizing a hydrophobic solid agricultural chemical in water or a hydrophilic medium, and suspending the resultant hydrophilicized extremely fine solid particles in a suspension medium. Japanese Examined Patent Publication No. 58-2,440 discloses a agricultural chemical suspension comprising a water-scant soluble solid agricultural chemical or a mixture of a water-scant soluble solid agricultural chemical with a water-soluble solid agricultural chemical, a surfactant, a water-soluble high molecular weight compound and water, and having a preparation viscosity of 200 to 500 cP at a temperature of 20.degree. C. Japanese Unexamined Patent Publication No. 57-58,601 discloses an agricultural chemical suspension comprising a agricultural chemical material insoluble or scant soluble in water or an organic solvent, a surfactant, xanthane gum and water. Japanese Unexamined Patent Publication No. 2-111,703 discloses an agricultural chemical suspension comprising an agricultural chemical material insoluble or scant soluble in water, a surfactant, a water-soluble biopolymer and water. Also, Japanese Examined Patent Publications No. 7-47,521, No. 7-47,522, No. 64-7,041, No. 63-58,802 and No. 6-78,202 disclose aqueous agricultural chemical suspensions containing a herbicide-active material or a biocide-active chemical and a surfactant.
Japanese Unexamined Patent Publication No. 9-52,810 discloses an aqueous emulsion having a reduced danger of ignition in production, transportation and storage. In this emulsion, as an emulsifying agent, polyoxyethylene-polyoxypropylene block copolymer is preferably used. Also, Japanese Unexamined Patent Publication No. 6-92,801 and Japanese Patent No. 2593,886 disclose a processes for producing a suspoemulsion containing two or more effective components greatly different in physico-chemical properties from each other, and report that the preparation of the suspoemulsion from the above-mentioned two or more components has been generally considered difficult.
An agricultural chemical in the form of microcapsules as sustained release capsules for the purpose of extending the effect-retaining time is disadvantageous in that the preparation procedures are difficult and a difference in capsule thickness or in failure rate occurs between production lots. Therefore, it is very difficult to maintain the sustained release property of the microcapsulated chemical constant. Further, when the microcapsulating technology is applied to suspended chemicals, the capsule shalls may be broken during the capsule-forming process, and the capsule-forming cost is high.
On other hand, the suspended agricultural chemical having a high diffusing property must be produced from a water-scant soluble solid chemical in the presence of a surfactant (emulsifier) and water by grind-pulverizing the solid chemical. This production requires a long time and much labor. Also, in this process, the emulsifier needs an organic solvent which may cause the environment to be poluted, and the effective component may crystallize during storage. Even in an agricultural chemical in improved microcapsules, the organic solvent is contained as an indispensable component. In a suspoemulsion chemical comprising a mixture of a emulsion system and a suspension system, to prevent a phase separation and a hard caking, it is indispensable to finely pulverizing the suspended solid particles and to add a thixotropic agent thereto. When the agricultural chemical having a high diffusing property and produced by the above-mentioned process is scattered in a rice paddy, the effective component in the chemical rapidly diffuses and an extension of the effect-retaining time cannot be expected.
An object of the present invention is to provide a process for producing a solvent-less O/W type emulsion having a high storage stability and capable of being diluted with a large amount of water with a high stability with a low cost.
The solvent-less O/W type emulsion of the present invention can contain two or more effective components which are greatly different in physical and properties from each other without need of assistance of an organic solvent.
Also, the solvent-less O/W type emulsion of the present invention may have a sustained release property. Further, the solvent-less O/W type emulsion of the present invention can contain a suspension of a solid particles with a high stability.
The solvent-less O/W type emulsion of the present invention is utilizable for wide various uses of the agricultural, pharmaceutical and cosmetic fields.